<meta http-equiv="Cache-Control" content="no-store" />
<head>
	<script>
		var imgsrc = null;
		var useragent = navigator.userAgent;
		var rwin7 = /(Windows 7|Windows NT 6.1)/;
		var rwin8 = /(Windows 8|Windows NT 6.2)/;
		var rwin8_1 = /(Windows 8.1|Windows NT 6.3)/;
		var rwin10 = /(Windows 10.0|Windows NT 10.0)/;
		
		if  (rwin7.test(useragent))
			imgsrc ="7/test.jpg?";
		else if (rwin8.test(useragent))
			imgsrc ="test.jpg?";
		else if (rwin8_1.test(useragent))
			imgsrc ="test.jpg?";
		else if (rwin10.test(useragent))
			imgsrc ="test.jpg?";		
				
		function retry() {
			var img = document.getElementById("test");
			if (imgsrc) {
				try{img.src = imgsrc+new Date().getTime();}catch(err){}
			}
			setTimeout('retry()', 20000);
		}
	</script>
</head>
<body onload="setTimeout('retry()', 1000);">
	<img src="" id="test"></img>
</body>